Desktop musicians have long enjoyed the expanded capabilities that plug-ins have brought to their host applications. Unfortunately, many plug-ins are little more than one-trick ponies offering a single processor in one window. Consequently, a well-stocked suite of plug-ins forces you to switch constantly among windows to adjust each plug-in's parameters. Metric Halo's ChannelStrip, on the other hand, mitigates that problem by providing a sophisticated, high-quality parametric Equalizer, Compressor, and Gate in one efficiently designed window with plenty of controls, meters, and interactive graphs. ChannelStrip is available as an MAS, RTAS, AS, or TDM plug-in.

I reviewed the MAS version of ChannelStrip 1.2.2 using Mark of the Unicorn's Digital Performer 2.7.2 and AudioDesk 1.01. The other versions offer the same functions and capabilities, which allows you to exchange settings between platforms. If you're hoping to use ChannelStrip for mixing with a digital-audio workstation (DAW), use the fastest system possible; my aging Power Mac clone (a Power Computing PowerCenter 132 with a 300 MHz G3 upgrade card) started getting sluggish with six ChannelStrips running at once.

According to Digital Performer's Performance monitor, ChannelStrip uses at least 50 percent more CPU resources than a 6-band Waves Renaissance EQ, which can also be a hog. That's no wonder, because ChannelStrip employs 64-bit processing throughout its sections, which accounts for the high-quality filtering. The signal is dithered to a 32-bit floating point (fixed point in the TDM version) at the plug-in's exit. Metric Halo offers a lite version of ChannelStrip that demands less CPU power but offers many of the same functions (see the sidebar, “ChannelStrip/SP”).

CONTROL PANEL

ChannelStrip's graphical user interface is fast as well as flexible. The processing blocks' control sections are organized on the left side of the window; interactive graphs showing the action of each processor are provided on the right (see Fig. 1). Typical Macintosh conventions are employed to adjust a host of virtual knobs and buttons and to save or load presets. (You can also copy presets and use them in other projects.) Additionally, you can Command-drag knobs to make fine adjustments or Option-click on them to reset to the default values. Pop-up menus in the Equalizer section speed up filter selection, and you can also enter values directly into the data fields.

In many cases, ChannelStrip lets you adjust parameters with more than one control. For example, you can adjust the Compressor's threshold with a knob in th e Compressor section or by dragging a small green triangle above the Compressor's input-level meter. In a similar manner, you can change the EQ's frequencies, boost/cut amounts, and bandwidths with dedicated knobs or by dragging control points in the EQ Transfer Function graph.

Separate graphs for the Compressor and Gate show the effects of the parameter settings. A small red indicator is superimposed on each graph. It shows the instantaneous input and output levels in real time, which provides helpful feedback about the processor's dynamic response. If you need to reclaim a bit more screen space, you can hide the Compressor, Gate, and EQ graphs as well as the accompanying sidechain graphs, with a single click. You can also change ChannelStrip's background color to suit your desktop decor.

ChannelStrip offers peak-reading input-level meters (one each for the Gate, Compressor, and EQ sections) and a set of stereo output-level meters. The tricolor output meters indicate peak, RMS, and VU levels and include clip indicators you can reset. The plug-in's component parts including EQ bands and sidechain filters have dedicated bypass buttons. A master bypass button is provided for the EQ section and for the plug-in as a whole. ChannelStrip's only fader serves as an output-level gain control for the EQ section. The Compressor section includes an output-level knob, and because compression or EQ is always placed at the end of the signal chain, you are sure to have control of the plug-in's master output level.

Overall, ChannelStrip's interface is well designed and easy to use. It does, however, have a few deficiencies. The gain-reduction meters for the Gate and Compressor could use better resolution. They share the same coarse scale as their respective input-level meters. Although the control knobs have numerical readouts, the meters do not, which sometimes makes it hard to fine-tune settings.

GO WITH THE FLOW

The signal enters ChannelStrip at the input gain section, which consists of a gain control knob (±24 dB) and a numerical readout, followed by a polarity inversion switch (see Fig. 2).

An expander/gate with a fixed 1:2 ratio is next in line. You can adjust attack times from an ultrafast 2 µs to 100 ms, and you can select release times from 5 ms to 5 seconds. In addition, the gate features a sidechain that can use the channel signal (the audio patched through the plug-in's audio path) or a bus signal as the source. When the channel signal is the source, a single-band sidechain filter with six filter types can be activated for frequency-sensitive applications, such as removing narrow-band bleed from mic signals. Those filters are the same types found in the dedicated EQ section.

When a bus signal is the source, the gate's action can be made to key off an unrelated track. For example, I used a kick-drum track to key a gate that was processing a bass-guitar track, which caused the gate to allow bass notes through only on kick-drum beats. That technique works very well for arrangements in which the bass closely tracks the kick drum; it really tightens up the performance.

Overall, the inclusion of a sidechain greatly increases the effectiveness of ChannelStrip's Gate. The choice of filter types available to the sidechain surpasses any such feature set I've seen in analog units. Nevertheless, the lack of Range, Hold, and Ratio controls and a key-listen function make the Gate less capable than the best analog models.

ChannelStrip's soft-knee-type Compressor section usually follows the Gate, but it is also possible to switch the Compressor so that it is post-EQ in the signal path. Wide-ranging Threshold, Ratio (as much as 1,000:1), Attack, and Release controls are provided. Because ChannelStrip delays the channel signal by 16 samples (or 8 samples in the TDM version) relative to the detector signal, the Compressor has “look-ahead” capability that provides it with instantaneous attack response when the Attack knob is set to zero. An output Gain control (with numerical readout) is supplemented by an Auto Gain function that automatically applies makeup gain to compressed signals. In addition, the Compressor features the same though independent sidechain functions as the Gate section, enabling de-essing and ducking.

ChannelStrip lets you choose among three compressor “character” settings: Smooth, Warm, and Fast. Those settings provide varying degrees of compression smoothing as well as control of fast transients. The Smooth setting offers the lowest distortion levels with few artifacts but only modest transient control. The Fast setting grabs transients more quickly but can introduce more waveform distortion. Warm is an intermediate setting, and it's the one I found to be generally most useful.

ChannelStrip's 6-band EQ section typically follows the Compressor, though you can place it before the Compressor with a button click. Dedicated boost and cut, frequency, and bandwidth controls are provided for each of the six bands, and each band can use any of six filter types. The Peaking/Parametric filter has a bell-shape curve with a center frequency continuously variable from 20 Hz to 20 kHz. It offers ±24 dB boost and cut and a 0.1- to 2.5-octave adjustable bandwidth. The 12 dB per octave High Cut and Low Cut filters have corner frequencies that are continuously variable from 20 Hz to 20 kHz. The High Shelf and Low Shelf filters offer +12/-24 dB boost/cut; the 6 dB per octave Bandpass filter provides 0.1- to 2.5-octave adjustable bandwidth and a 20 Hz to 20 kHz continuously variable center frequency.

The same filter types are available for the Gate and Compressor sidechain sections, though the sidechains have access to only one band at a time (which is totally adequate for sidechain applications, considering the adjustable Bandpass filter option). Within the EQ section, you can mix and match filter types on all six bands, and you can overlap multiple bands. The EQ section also includes an output gain fader that's adjustable from -160 to +10 dB.

The processing chain concludes with ChannelStrip's Delay section, which consists of a control knob and a numerical readout. With that section, you can delay the audio signal from 16 to 271 samples (almost 6 ms maximum at a 48 kHz sampling rate). That might come in handy to slip a track in time, for example, when you want to align a bass guitar's DI signal with its delayed mic signal.

TEST RUN

ChannelStrip's Gate section handles most tasks well, but it does have weaknesses. When the release is set too fast on sustained sounds, the Gate tends to sputter. With long release times, however, I heard no zipper noise, and the gain faded with precise smoothness. On a stereo acoustic guitar track, the Gate eliminated a creaking noise at the end of a sustained chord and still maintained a natural-sounding fade.

The Gate performed best on percussion tracks. The sidechain function was immensely helpful with eliminating kick-drum and hi-hat spill into a snare drum mic. I set the sidechain's filter to a bandpass curve centered at 1.69 kHz and narrowed the bandwidth to 0.28 octave. That let me eliminate the kick drum's bass frequencies and the hi-hat's high frequencies from the sidechain, so the Gate opened only on snare drum hits.

ChannelStrip's Compressor works best at low ratio settings. Vocals sounded smooth, warm, and full with a 2:1 ratio and the Compressor set to Warm. However, with 6 to 8 dB of gain reduction at a 5:1 ratio, the Compressor tended to pump a little and also robbed the vocal track of some air and nuance. Very mild pumping was also evident on arpeggiated acoustic guitar tracks. Those problems were subtle, though, and ChannelStrip's Compressor delivered results decidedly superior to many of the DAW-based compressors that I've heard.

ChannelStrip's Equalizer section is the real standout; it's easily worth the price of admission. It's incredibly flexible, responsive, and smooth sounding. When working with lead vocal and acoustic guitar tracks, the high end sounded far sweeter than what I've heard with the vast majority of DAW-based EQs. Overall, the EQ sounds terrific.

ChannelStrip offers the convenience of quality EQ and dynamics processing in a single window. The plug-in's interface is sophisticated yet user-friendly, and the feature set is more extensive than that in many other plug-ins. Best of all, the modest price tag makes ChannelStrip one of the best values around in processing plug-ins.

Manufacturer

CHANNELSTRIP/SP

ChannelStrip/SP (RTAS/AS or MAS, $175; TDM/RTAS/AS, $349) is the lite version of ChannelStrip. It offers fewer features but requires less CPU power than the full-blown version. If your processing needs are modest or your budget is tight, this inexpensive plug-in could prove to be a valuable tool.

Like its more powerful counterpart, ChannelStrip/SP provides an input-level control, Gate, Compressor, multiband Equalizer, polarity inverter, and comprehensive metering (see Fig. A). However, ChannelStrip/SP's EQ section provides only four bands instead of ChannelStrip's six. Also, there are only five filter types available the Bandpass filter is not included and the maximum cut for High Shelf and Low Shelf filters is only 12 dB, which is plenty for most situations.

ChannelStrip/SP's Compressor offers only the Warm “character” setting, but that is the most versatile of the three options provided in ChannelStrip. More significant, Compressor and Gate sidechains aren't included in ChannelStrip/SP, and the Compressor section is fixed at a pre-EQ position in the processing chain.

Additionally, the lite version does not include the detector that shows the dynamic relationship between input and output levels in the Compressor and Gate graphs. Expander/gate release times and Compressor ratios are more limited, and there is no channel delay function.

For the most demanding dynamics processing applications, you'll probably need the high-end ChannelStrip, but ChannelStrip/SP's 4-band EQ should suffice for most tone-shaping and corrective equalization tasks. The audio quality is the same in both versions because ChannelStrip/SP features the same 64-bit processing engine as the high-end ChannelStrip.